Processing audio input signals

Abstract

A method of reproducing a stereo output signal (having a left field and a right field) represented as digital samples such that said stereo signal emulates the production of said audio signal from a specified audio source location relative to a listening source location (an indicated location). A left channel signal is produced by convolving an audio input signal with a broadband response file, selected from a plurality of stored files derived from empirical testing, dependant upon the indicated location. A right channel signal is also produced in this way. The left and right channel signals are each duplicated for playing through each of a plurality of displaced left field loudspeakers and displaced left field loudspeakers displaced right field loudspeakers respectively. Apparatus for reproducing a stereo output signal. A data storage facility having a stereo output signal.

The invention claimed is:  
     
       1. A method comprising reproducing a stereo output signal
 having a left field and a right field and represented as digital samples, said stereo signal emulating 
 the production of an audio signal from a 
 virtual audio source location relative to a listening location, said listening location having a left 
 listening position and a right listening position corresponding to the left and right ears of a typical 
 listener; said method using audio playback equipment comprising a first input device, a second 
 input device, a plurality of displaced left field loudspeakers and a plurality of displaced right field 
 loudspeakers; and said method further comprising the steps of: 
 receiving by said first input device a left channel signal and a right channel signal; produced by convolving an audio input signal with a left field broadband response file selected from a plurality of stored files derived from empirical testing and describing the impulse response of a left ear to a sound emitted from said indicated location; 
 playing said left channel signal through each of said plurality of displaced left field loudspeakers; and 
 playing said right channel signal through each of said plurality of displaced right field loudspeakers; 
 wherein said left channel signal and said right channel signal are produced by way of the following process: 
 receiving an audio input signal, an indication of the virtual audio source location, and an indication of the distance between the left listening position and the right listening position; 
 determining said left and right listening positions, based on said listening location and said indication of distance 
 determining a first direction from said indicated location to said left listening position and a second direction from said indicated location to said right listening position, wherein the indicated location is manually indicated or indicated in response to operation performed within a computer game; 
 selecting a left field broadband response file describing the impulse response of a left ear to a sound emitted from said first direction; 
 selecting a right field broadband response file describing the impulse response of a right ear to a sound emitted from said second direction; 
 convolving said audio input signal with said selected left field response file to produce the left channel signal; 
 convolving said audio input signal with said selected right field response file to produce the right channel signal. 
 
     
     
       2. A method according to  claim 1 , wherein said audio input signal is a live signal, a recorded signal or a synthesised signal. 
     
     
       3. A method according to  claim 1 , wherein said left channel signal is duplicated for each of said plurality of displaced left field loudspeakers and said right channel signal is duplicated for each of said plurality of displaced right field loudspeakers. 
     
     
       4. A method according to  claim 1 , wherein said plurality of loudspeakers includes an arrangement of loudspeakers located relative to said listening location, at which:
 the forward facing direction of a listener at said listening location is identified as being at zero (0) degrees azimuth, and 
 said arrangement of loudspeakers includes: 
 a first left loudspeaker positioned at minus thirty (−30) degrees azimuth, 
 a second left loudspeaker positioned at minus one hundred and ten (−110) degrees azimuth, 
 a first right loudspeaker positioned at plus thirty (+30) degrees azimuth, and 
 a second right loudspeaker positioned at plus one hundred and ten (+110) degrees azimuth. 
 
     
     
       5. A method according to  claim 1 , wherein said plurality of broadband response files stored for at least one of said left field and said right field are produced by a method comprising the steps of:
 locating a human subject in an anechoic chamber such that the left ear or the right ear respectively is at the centre of an originating region, 
 locating an audio microphone adjacent the ear canal of the left ear or the right ear respectively of said human subject, 
 locating a sound source in said anechoic chamber, 
 playing an audio output for each of a plurality of test positions, said audio output including a plurality of frequencies, 
 the co-ordinates of said test positions are identified by: 
 a common radial distance from the centre of the originating region, 
 degrees elevation from the centre of the originating region, said centre determined to be at zero (0) degrees elevation, and 
 degrees azimuth from a predetermined position at zero (0) degrees elevation; 
 recording the resulting microphone output for each test position, 
 deriving a reference signal for each test position from said microphone output recorded for each test position, 
 deriving an originating signal from at least one reference signal, and 
 deconvolving the reference signal for each test position with said originating signal to produce a broadband response file for each test position for said first ear. 
 
     
     
       6. A method according to  claim 5 , wherein said originating signal is derived by a method comprising the steps of:
 selecting a first reference signal derived from said microphone output recorded for the test position at minus thirty (−30) degrees azimuth, zero (0) degrees elevation or plus thirty (+30) degrees azimuth, zero (0) degrees elevation respectively, 
 deconvolving said first reference signal with said audio output to produce a first impulse response signal, 
 selecting a second reference signal from said microphone output recorded for the test position at minus one hundred and ten (−110) degrees azimuth, zero (0) degrees elevation or plus one hundred and ten (+110) degrees azimuth, zero (0) degrees elevation respectively, 
 deconvolving said second reference signal with said audio output to produce a second impulse response signal, and 
 combining said first impulse response signal and said second impulse response signal to produce said originating signal. 
 
     
     
       7. A method according to  claim 5 , wherein a broadband response file is stored for at least 770 test positions for each of said first ear and the other second ear of the human subject. 
     
     
       8. A method according to  claim 5 , wherein a plurality of broadband response files is stored for each test position, each of the plurality of broadband response files for a test position relating to a different subject material or environment. 
     
     
       9. A method according to  claim 5 , wherein said audio output from said sound source at least one sound having a frequency greater than twenty (20) kilohertz. 
     
     
       10. Apparatus for reproducing a stereo output signal having a left field and a right field and represented as digital samples, said stereo signal emulating the production of an audio signal from a virtual audio source location relative to a listening location, said listening location having a left listening position and a right listening position corresponding to the left and right ears of a typical listener;
 the apparatus comprising a first input device, a second input device, a processing device, a plurality of displaced left field loudspeakers and a plurality of displaced right field loudspeakers, wherein: said first input device is configured to receive a left channel signal and a right channel signal; said processing device is configured to distribute said left channel signal for playback through each of said plurality of displaced left field loudspeakers, and distribute said right channel signal for playing through each of said plurality of displaced right field loudspeakers; 
 wherein said left channel signal and said right channel signal are produced by way of the following process: 
 receiving an audio input signal, an indication of the virtual audio source location, and an indication of the distance between the left listening position and the right listening position; 
 determining said left and right listening positions, based on said listening location and said indication of distance; 
 determining a first direction from said indicated location to said left listening position and a second direction from said indicated location to said right listening position, wherein said indicated location is manually indicated or indicated in response to operations performed within a computer game; 
 selecting a left field broadband response file describing the impulse response of a left ear to a sound emitted from said first direction; 
 selecting a right field broadband response file describing the impulse response of a right ear to a sound emitted from said second direction: 
 convolving said audio input signal with said selected left field response file to produce the left channel signal; 
 convolving said audio input signal with said selected right field response file to produce the right channel signal. 
 
     
     
       11. Apparatus according to  claim 10 , wherein said audio input signal is a live signal, a recorded signal or a synthesised signal. 
     
     
       12. Apparatus according to  claim 10 , wherein said left channel signal is duplicated for each of said plurality of displaced left field loudspeakers and said right channel signal is duplicated for each of said plurality of displaced right field loudspeakers. 
     
     
       13. Apparatus according to  claim 10 , wherein said plurality of loudspeakers includes an arrangement of loudspeakers located relative to a listening position, at which:
 the forward facing direction of the listener is identified as being at zero (0) degrees azimuth, and 
 said arrangement of loudspeakers includes: 
 a first left loudspeaker positioned at minus thirty (−30) degrees azimuth, 
 a second left loudspeaker positioned at minus one hundred and ten (−110) degrees azimuth, 
 a first right loudspeaker positioned at plus thirty (+30) degrees azimuth, and 
 a second right loudspeaker positioned at plus one hundred and ten (+110) degrees azimuth. 
 
     
     
       14. Apparatus comprising a non-transitory data storage medium having a stereo output signal having a left field and a fight field and represented as digital samples, said stereo signal emulates the production of an audio signal from a virtual audio source location relative to a listening location, said listening location having a left listening position and a right listening position corresponding to the left and right ears of a typical listener; in which a left channel signal and a right channel signal have been produced by way of a process comprising:
 receiving an audio input signal, an indication of the virtual audio source location, and an indication of the distance between the left listening position and the right listening position wherein the indicated location is manually indicated or indicated in response to operations performed within a computer game; 
 determining said left and right listening positions, based on said listening location and said indication of distance; 
 determining a first direction from said indicated location to said left listening position and a second direction from said indicated location to said right listening position; 
 selecting a left field broadband response file describing the impulse response of a left ear to a sound emitted from said first direction:. 
 selecting a fight field broadband response file describing the impulse response of a right ear to a sound emitted from said second direction; 
 convolving said audio input signal with said selected left field response file to produce the left channel signal; 
 convolving said audio input signal with said selected fight field response file to produce the right channel signal. 
 
     
     
       15. A non-transitory data storage facility according to  claim 14 , wherein:
 said left channel signal is duplicated for distribution for playback through each of a plurality of displaced left field loudspeakers, and 
 said right channel signal is duplicated for distribution for playback through each of a plurality of displaced right field loudspeakers. 
 
     
     
       16. A non-transitory data storage facility according to  claim 14 , wherein said audio input signal is a live signal, a recorded signal or a synthesised signal.